Automatic and semi-automatic weapons have employed a variety of gas-operated systems utilizing the pressure of combustion gases released upon firing of a round to engage and displace a piston operatively associated with a bolt mechanism to unlock, extract, eject, feed, reload, lock and cock before firing the next round. Most of the prior art systems employ a piston-cylinder arrangement mounted parallel with the gun barrel, although U.S. Pat. No. 4,817,496 proposes utilizing the gun barrel itself as an in situ piston with large and small outer diameters being operatively associated with a sliding cylinder having corresponding large and small linear diameter portions mounted coaxially with and displaceable relative to the gun barrel. Such a system is subject to undue thermal expansion of the multi-diameter gun barrel negatively affecting operability and reliability. Moreover, such a system having a long stroke requires elaborate machining of the gun barrel outer surfaces and the cylinder for effecting the comparatively long stroke of the cylinder.
There exists, therefore, a need to provide a novel system that overcomes the above-noted and other drawbacks of the existing systems.